Wafer-type devices may be processed in a number of ways for the purpose of adding and/or removing materials to the surface of the wafer. Specifically, coatings may be applied selectively or over the entire wafer surface, and material may be uniformly or selectively removed instead of being applied or in addition to it. In particular, selective removal may be done in accordance with a predetermined pattern to provide specific surface features. The present invention was developed for its specific application in processing semiconductor wafers. Semiconductor wafer processing typical includes the application of coating materials in layers on the wafer substrate and/or the selective removal of material by an etching process.
Wafer etching typically requires that the surface of a wafer (including any number of coating layers) be exposed to an etchant, such as may comprise any of various known chemicals, including a number of acids. If the etchant is provided in the form of a gas, the etching technique is considered a dry or vapor phase processing technique. If, on the other hand, the etchant is provided as a liquid, the technique is characterized as a wet processing technique. Furthermore, in some cases, it is desirable to rinse the wafer surface after etching so as to remove soluble residues from the surface of the wafer. Specifically, it is known to use a wet etching process combined with a wet rinsing operation. Similarly, vapor phase etching and cleaning techniques have also been used together.
Moreover, the assignee of the present invention has commercialized certain vapor phase etch/wet rinse process systems, which cleaning systems have been commercially available under the trade name EXCALIBUR.RTM., including a multi-vapor processor (MVP) and an in-situ rinse processor (ISR). An advantage of the Excalibur system chamber is that both the vapor phase etching and wet rinsing can be conducted within a single process chamber. That is, it is not required that the vapor phase etching be done is a first chamber followed by the transfer of the wafer into a second chamber for conducting the wet rinsing.
Specifically, as shown in the FIGS. 1, 2, and 3, an etch position, a transfer position, and a rinse position are schematically illustrated within a single process chamber in that respective order. The process chamber basically comprises a chamber bell 1 and a lower chamber assembly 2. A wafer 3 is supported on a rotatable chuck 4 that is driven by a spin motor 5. The lower chamber assembly 2 is also relatively movable with respect to a pedestal 6 that rotatably supports the chuck 4. A gas inlet line 7 permits the introduction of gas into the internal cavity of the system chamber, and a liquid inlet conduit 8 facilitates dispensing rinse liquid on the wafer surface after etching. The dispensed liquid can collect in the rinse bowl section of the internal chamber so as to exit from the internal chamber though appropriate drains.
The operation between the etch, transfer and rinse positions of the Excalibur system chamber is based upon two different relative movements. The first movement is the relative movement between the chamber bell 1 and the lower chamber assembly 2. The second movement is the relative movement between the pedestal 6 and the lower chamber assembly 2. In the illustrated system, the chamber bell 1 moves with the lower chamber assembly 2 during this second movement.
For operation, a wafer 3 is loaded onto the rotatable chuck 4 while in the transfer position that is illustrated in FIG. 2 where the chamber bell 1 is separated from the lower chamber assembly 2. This loading can be conducted by a known robotic system that can move a wafer in and out of the process chamber and set it down on the chuck 4 (i.e. a robot with three axis movement). As also shown in FIG. 2, gas, such as nitrogen, may be introduced at this time though the gas inlet line 7 for system purging and to maintain a clean gas environment near the wafer 3. Then, for etching, the chamber bell 1 is moved to a position against the lower chamber assembly 2. Between them, a fluoropolymeric o-ring is provided to generate a seal between the chamber bell 1 and the lower chamber assembly 2. In particular, a driver, such a pneumatic pancake cylinder, provides a first motion system that moves the chamber bell 1 against the lower chamber assembly 2 so as to provide a sufficient crush force to create a efficient seal. As shown in FIG. 1, etchant gas can be then introduced though the gas inlet line 7 to perform the etching operation in accordance with known vapor phase etching process techniques. Note also that in the FIG. 1 etch position the rinse bowl section of the internal chamber is substantially closed from the etching portion of the internal chamber by way of the interaction of pedestal 6 and the lower chamber assembly 2. Thus, the etching portion of the internal chamber is substantially isolated during the etching operation from the rinse bowl section where droplets of rinsing fluid may still be present on the rinse bowl surfaces from a prior rinsing operation. The desire to isolate the etching and rinse bowl sections from one another depends on the etchant used, machine thoughput requirements, and wafer application process tolerances. After etching, the rinse operation is conducted by raising the chamber assembly (comprising the chamber bell 1 and the lower chamber assembly 2) while leaving the wafer chuck 4 at the same elevation, thus effectively lowering the wafer 3 to a rinse position within the rinse bowl section of the internal chamber. Thus, rinsing liquid, such as water, can be dispensed onto the wafer via the liquid inlet conduit 8, and it can leave the internal process chamber though its rinse bowl section that leads to drains. By positioning the wafer in the rinse position, the rinsing liquid can be dispensed on the wafer with minimal exposure of the liquid to the internal walls of the etching portion of the internal process chamber. Clean gas is also provided though the gas inlet line 7 during the rinsing operation for purging any gas etchant remaining in the internal chamber along with the rinsing liquid though the drains. Once the rinse operation is complete, the lower chamber assembly 2 can be lowered relative to the pedestal 6 so as to position the wafer 3, once again, in the transfer position of FIG. 2, where it is again accessible by the system robot. The lower chamber assembly 2 is movable by a second motion system, such as may comprise another pneumatic cylinder. The lower chamber assembly 2 may be lowered with the chamber bell 1 followed by the chamber bell 1 being subsequently raised to the transfer position. Or the lower chamber assembly 2 may be lowered while the chamber bell 1 is maintained in an up position so as to make the transfer position.
Another similar system has also been developed by the assignee of the present intervention, and this system is described in U.S. Pat. No. 5,820,692 granted on Oct. 13, 1998 to Baecker et al. In this system, wafers are transferable into and out of the system chamber while being surrounded within a vacuum chamber. Also, the relative movement between the pedestal and the lower chamber assembly is effected by moving the pedestal up and down while maintaining the lower chamber assembly in a fixed position. A chamber bell is opened and closed by a first cylinder while the pedestal moves the wafer supporting chuck between the etch position and a rinse position as driven by a second cylinder assembly. The transfer position is defined by lifting the chamber bell from the lower chamber assembly. So, a seal is also provided for sealing the chamber bell to the lower chamber assembly under a crush force of the first cylinder to define an etching portion of the process chamber.
Although each of the systems described above provide effective means for etching and rinsing wafers without each operation negatively affecting the other, two motion systems are required. The use of such plural motion systems requires that significant alignment structure and adjustment features be provided to assure accurate alignment and proper definition of the etching and rinse positions. Moreover, by utilizing a chamber bell that is openable and closable, not only must a seal be provided between them, the first motion means must be precisely controlled and capable of a force of sufficient magnitude to create a crush force for making an effective seal. This sealing ability can change over time because of repetitive crushing of the O-ring and exposure thereof to the environment. Occasional adjustment of the first motion means and/or replacement of the O-ring might be required.
Also, removing the chamber bell completely from the lower chamber assembly to permit wafer transfer opens the entire internal process chamber to the air of the surrounding environment. Thus, surrounding air that may not be controlled sufficiently for temperature and humidity content, for example, might adversely affect the process operations. No matter how effectively the internal process chamber conditions are controlled by the system, opening the internal process chamber completely can introduce a variable into the process. Moreover, fully opening the internal process chamber increases the likelihood that chemical vapors (such as etchant vapors) may be emitted into the surrounding environment.